Sex differences in the development of hypertension and cardiovascular disease have been well described in humans and in animal models. Low dose AngII infusion is known to induce a neurogenic hypertension via CNS actions on circumventricular organs in the brainstem and hypothalamus. An increasing body of evidence has shown that Angll central and peripheral effects involve activation of reactive oxygen. Similarly, central peripheral studies with estrogen and testosterone have shown that many of their cardiovascular related effects may be related their modulation of the generation of reactive oxygen species (ROS) and nitric oxide (NO). Recent data from our laboratory have shown that low-dose infusion of AngII results in hypertension WT male mice but not in intact WT females. Further, we have new preliminary data showing that AngII induced hypertension in males is blocked by central infusions of the adrogen receptor flutamide and by central infusion of the superoxide dismutase (SOD) mimetic tempol and that males show greater levels of intracellular ROS in CVO neurons following Ang II long-term infusion than females. This proposal will use brainstem slices of circumventricular organs key to AngII hypertension, state-of-the-art imaging techniques, real-time RT-PCR, adeno-vector gene transfer and telemetry measurements of conscious blood pressure recordings to test the general hypothesis that sex and sex steroids modulate the central actions of Angll via interactions with free radical and NO generating pathways within the circumventricular organs of the brainstem and hypothalamus. This hypothesis will be tested with 4 specific aims: Specific Aim 1. Determine the roles of nNOS and SOD on AngII induced increases in [Ca++]i in the brainstem and forebrain CVO brain slices from male and female mice. Specific Aim 2: Determine the effects of sex and sex steroids on AngII induced release of intracellular ROS in the brainstem and forebrain CVOs of male and female mice. Specific Aim 3: Determine the effects of sex and sex steroids on expression of SOD, nNOS and AT1 receptors in the brainstem and forebrain CVOs of males and females mice. Specific Aim 4: Determine the role of SOD and nNOS in AngII induced hypertension in WT males and females.